Magnetic boresighter

ABSTRACT

A rifle boresighter having a front adapted to face a rifle user after the boresighter has been attached to a rifle and a rear adapted to face away from the user after the boresighter has been attached to a rifle. The boresighter includes a post defining a receptacle that retains a magnet and a tubular housing having a front and a rear coincident to the front and rear of the boresighter and being supported by the post. A collimating lens is supported at the front of the tubular housing, a reticle supported in the tubular housing and a light window in the rear of the tubular housing. Also, the tubular housing is supported by the post approximately midway between it front and its rear, thereby providing a balanced load to the magnet.

BACKGROUND

A magnetic boresighter is a device that magnetically attaches to the front of a rifle barrel and permits a user to align the pointing direction of his scope to the angle of the front of the rifle barrel. Because the bullet exits the barrel traveling in the direction of the end of the barrel, this is a good method of aligning a scope.

To do this, the typical boresighter includes a reticle, permits light to enter at the end farthest from the scope and collimates this light, so that the reticle is effectively placed at an infinite range, straight ahead of the rifle barrel. In order for the reticle to be visible to someone looking through the scope, however, the collimated light, traveling in a straight line, must be able to enter the scope objective lens. So if there is no overlap between a cylinder extending straight back from the collimator lens and the objective lens of the scope, it will not be possible to use the boresighter. As scopes may be installed at different distances above the rifle breach block, a magnetic boresighter requires some flexibility in placement, in order to be able to accommodate a range of scope installations.

Unfortunately, currently available magnetic boresighters tend to be fairly expensive and may not attach magnetically to every rifle barrel end. One boresighter includes a magnet for attaching to the end of a rifle barrel, but the optical portion of the boresighter is arranged all forward of the magnet when attached to a rifle, introducing some instability to the attachment. Also, currently available boresighters feature a vertically extending longitudinal magnet, which is about 50 mm (2 inches) in vertical extent. Although this may help accommodate a wide range of scope installations, it also drives up the expense of boresighter manufacturing.

SUMMARY

The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.

In a first separate aspect, the present invention may take the form of a rifle boresighter having a front adapted to face a rifle user after the boresighter has been attached to a rifle and a rear adapted to face away from the user after the boresighter has been attached to a rifle. The boresighter includes a post defining a receptacle that retains a magnet and a tubular housing having a front and a rear coincident to the front and rear of the boresighter and being supported by the post. A collimating lens is supported at the front of the tubular housing, a reticle supported in the tubular housing and a light window in the rear of the tubular housing. Also, the tubular housing is supported by the post approximately midway between it front and its rear, thereby providing a balanced load to the magnet.

In a second separate aspect, the present invention may take the form of a rifle boresighter, including a post defining a receptacle, retaining a magnet and a tubular housing supported by the post. A collimating lens assembly is supported at the front of the tubular housing, a reticle supported in the tubular housing and a light window in the rear of the tubular housing. Also, the magnet is roughened to provide frictional support against the front of a rifle barrel.

In a third separate aspect, the present invention may take the form of a boresighter that includes a magnet for attachment to the end of a rifle barrel, and optical assembly and a bridge connecting the two, and wherein the magnet has a vertical extent of less than 40 mm, thereby reducing the expense of the boresighter while accommodating most rifle and scope assembly geometries.

In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a magnetic boresighter according to the present invention, installed onto the front of the barrel of a scope-bearing rifle.

FIG. 2 is a perspective view of a boresighter according to the present invention.

FIG. 3 is a lengthwise sectional view of a boresighter according to the present invention.

Exemplary embodiments are illustrated in referenced drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a boresighter 10, according to the present invention, may be attached to the end of a rifle barrel 12 and used to help a user adjust the angle of a scope 14 relative to the pointing direction of the rifle barrel 12. To perform this operation the user looks through scope 14 and adjusts the angle of scope 14 until the reticle image presented by boresighter 10 and the reticle image presented by the scope 14 are mutually aligned. In this application, the front 16 of the boresighter 10 is defined as the end facing the user and the rear 18 is defined as the end further away from the user.

Referring to FIG. 3, to create a reticle image, boresighter 10 hosts an optical train within a tubular housing 20, including a reticle 22, a rear illumination window 24 and a collimator lens 26, which causes light to exit boresighter 10 in collimated form. The interior spaces 28 of housing 20 are broken into different widths, to prevent unwanted optical effects.

Referring to FIG. 2, a post 30 defining a round opening which retains a magnet 32 is provided to support the tubular housing 20 and its optical train at the end of the rifle barrel. Magnet 32 has a roughened front surface, having about 0.5 mm peak to valley surface variation, to provide frictional support for the boresighter as it sits at the end of the rifle barrel. Also, post 30 supports housing 20 near the longitudinal middle of housing 20, so that housing 20 presents a balanced load to post 20 and magnet 32.

Different rifle and scope assembly geometries have differing vertical displacements between the rifle center bore and the scope reticle center point. The boresighter collimates the light that is emitted through its front, toward the scope. Accordingly, as long as there is some horizontal straight line overlap between the boresighter optical train and the scope objective lens, the reticle image from the boresighter will theoretically appear to a user looking through the scope. But if there is only a very small overlap, the amount of light being received by the scope from the boresighter will be very small, so that the reticle from the boresighter will be very dim or even imperceptible. A boresighter is limited in the range of rifle/scope assembly geometries that it can accommodate by the vertical extent of the magnet used to attach the boresighter to the end of a rifle. Magnet 32 has a diameter of 25 mm, which, together with a collimating lens assembly diameter of 24.5 mm and a closest surface separation between magnet and collimating lens (a bridge) of 15 mm, accommodates most rifle and scope assemblies. The long magnets used in currently existing boresighters drive up the cost, making it impractical for some shooters to purchase a boresighter. Boresighter 10 addresses this problem by utilizing a smaller magnet, that can still work with most geometries. This breakthrough enables shooters who would not otherwise be able to afford a boresighter in order to properly align their scopes to rifle boresight, to do so.

While a number of exemplary aspects and embodiments have been discussed above, those possessed of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope. 

1. A rifle boresighter having a front adapted to face a rifle user after said boresighter has been attached to a rifle and a rear adapted to face away from said user after said boresighter has been attached to a rifle, said boresighter comprising: (a) a post defining a receptacle that retains a magnet; (b) a tubular housing having a front and a rear coincident to said front and rear of said boresighter and being supported by said post; (c) a collimating lens supported at said front of said tubular housing, a reticle supported in said tubular housing and a light window in said rear of said tubular housing; and (d) wherein said tubular housing is supported by said post approximately midway between it front and its rear, thereby providing a balanced load to said magnet.
 2. The boresighter of claim 1, wherein said magnet has a roughened front surface, to counteract the tendency of the magnet, and therefore, the boresighter to slide downwardly under the force of gravity while the boresighter is in use.
 3. A rifle boresighter, comprising: (a) a post defining a receptacle, retaining a magnet; (b) a tubular housing supported by said post; (c) a collimating lens assembly supported at said front of said tubular housing, a reticle supported in said tubular housing and a light window in the rear of said tubular housing; and (d) wherein said magnet is roughened to provide frictional support against the front of a rifle barrel.
 4. A boresighter that includes an optical assembly and a magnet for attachment to the end of a rifle barrel, said optical assembly connected to said magnet by a bridge, and wherein said magnet has a vertical extent of less than 40 mm, thereby reducing the expense of producing said boresighter while accommodating most rifle and scope assembly geometries.
 5. The boresighter of claim 4, wherein said magnet has a vertical extent of less than 35 mm.
 6. The boresighter of claim 4, wherein said magnet has a vertical extent of less than 30 mm.
 7. The boresighter of claim 4, wherein said magnet has a vertical extent of less than 27 mm.
 8. The boresighter of claim 4, wherein said magnet is elliptical, thereby providing sufficient greater width in the vertical middle, to accommodate a rifle barrel.
 9. The boresighter of claim 8, wherein said magnet is round.
 10. The boresighter of claim 4 having a round optical assembly attached and supported by a post attached to said magnet, sound round optical assembly having a round collimating lens at the front of said optical assembly and wherein said collimating lens has a diameter of less than 40 mm, reducing scope expense.
 11. The boresighter of claim 10 wherein said collimating lens has a diameter of less than 35 mm.
 12. The boresighter of claim 10 wherein said collimating lens has a diameter of less than 30 mm.
 13. The boresighter of claim 10, wherein said collimating lens has a diameter of less than 28 mm.
 14. The boresighter of claim 10, wherein said post has a length, such that the boresighter and said optical assembly are separated, at closest points, by between 12 and 20 mm.
 15. A boresighter that includes an optical assembly, including a collimating lens, and a magnet for attachment to the end of a rifle barrel, said optical assembly connected to said magnet by a bridge, and wherein said collimating lens has a diameter of less than 35 mm, thereby reducing the expense of producing said boresighter while accommodating most rifle and scope assembly geometries. 